Rod rolling method



June 9, 1964 o. PALMER ETAL ROD ROLLING METHOD Filed April 16, 1958United States Patent Ofiice 3,136,054 Patented June 9, 1964 3,136,054ROD ROLLING METHOD Oskar Palmer and Karl Gies, Dusseldorf, Germany,assignors to Baustahlgewebe G.m.b.H., Dusseldorf-fiberkassel, GermanyFiled Apr. 16, 1958, Ser. No. 729,005 Claims priority, applicationGermany Apr. 20, 1957 6 Claims. (Cl. 29-547) This invention relates 'tomethods of producing reinforceinent steel with transverse indentationson the peripheral surface thereof.

Whereas smooth rolled wire was once used for reinforcing concrete, thishas now for many years been superseded by rolled wire with a surfacepartly or wholly transverselyribbed, indented, twisted, or otherwisedeformed to establish a better bond with the concrete. Moreover, forimproving the peripheral properties of bars for reinforcing concrete,recourse has been had to hardening them, especially by means of colddeformation, such as stretching or twisting. However, it has been foundthat owing to the notch sensitivity of the steel the bending fatiguestrength of ribbed or indented reinforcing bars is adversely affected bythis cold deformation frequently to such an extent as to make them unfitfor use. The production of reinforcements of this kind, which firstseemed so promising, has therefore been widely discontinued.

In the special case of pre-stressed concrete and in many otherapplications, drawn wire is used to provide the reinforcement. Whereasin actual practice a smooth round section wire is nearly exclusivelyused, it has nevertheless already been proposed to provide the wiresurface with special profiles for improving the bond with the concretein much the same Way as does the ribbing on bars in ordinary reinforcedconcrete. The wires for pre-stressed concrete are thus formed forinstance with ribs by cold rolling the wire to forge the requireddeformations during or after the straightening process and after thewire has been drawn. However, such wires have not been successful. Thecold rolling deforms the circular section and gives rise to subsequentdifliculties when straightening or welding the wires and when weldingthe wires into a mesh inasmuch as additional strains are set up andwarping occurs. Moreover, the notch sensitivity of the wires, as alreadymentioned, so reduces their cold deformability, especially their bendingfatigue strength, that the rolled indentations must necessarily besoshallow that the bond in the concrete is scarcely improved or that thewire cannot be drawn down sufiiciently to secure the desired improvementin strength.

The present invention provides a simple and inexpensive method ofproducing a concrete reinforcing wire of a kind that will give anoptimum bond in concrete and at the same time retain excellent colddeformation characteristics, especially in regard to its bending fatiguestrength, in that the wire is subjected to compression stress in theperipheral zone and to tension stress in the core.

According to the invention, the wire is first provided, by rollingindentations into the same, with transverse rib-like surfaces forbonding with the concrete and is then drawn down through a wire-drawingdie or drag plate to a section which is less than that prior to ribbing.Preferably the process is performed on a round section wire which isfirst rolled in a shaping mill which forms grooves in opposite sides ofthe wire, said grooves leaving lands constituting the ribbing betweenthem. The rolling imparts an oval section to the wire. Alternatively, anoval-sectioned wire could be used ab initio. In any event, it isexpedient to form the ribs on the flatter sides of the oval crosssection. The advantage of the oval cross section is that, in drawing thewire through a die with a circular opening, the discontinuities in thesection will not interfere with the smooth passage of the wire throughthe die. Despite the presence of the ribs, no special difficulties willtherefore arise in the drawing. Further, to reduce the generation ofundue stress in the die, it is advisable to stagger the indentations oneither side of the wire in such manner that a land will always besituated diametrically opposite a groove in any one section. For thesame reason, the ribs may also be pitched obliquely in relation to theaxis of the wire, so that the wire cross section will be the same orsubstantially the same along the entire length of the wire. Indentationsmay also be formed in the wire when hot rolling the same.

By carefully choosing the depth of the indentations in accordance withthe reduction in section when drawing, it is possible to achieve anincrease in tensile strength in the surface regions which are colddeformed substantially the same as the increase in strength achieved inthe regions which are subject to cold deformation merely or chiefly bystretching. The rolling produces slight compression stresses on thesurface or in the peripheral zone of the wire while the die-drawingproduces substantial compression stresses in said zone and tensionstresses in the core or central zone.

It may be stated in this connection that, in the production of smoothtubes or bars, it is already known first to roll the material and thento draw it through a die in one operation. However, the object in thisknown procedure differs from that contemplated by the present proposalin that the known process is merely intended to remove the burrs and tocalibrate the material to an accurately determined dimension.

The invention will now be described with reference to the accompanyingdrawings in which:

FIG. 1 is a perspective view of a rolled wire as used for performing themethod according to the invention;

FIG. 2 is a similar perspective view of a ribbed wire produced by coldrolling the rolled wire shown in FIG. 1;

FIG. 3 is a perspective view illustrating a reinforcing wire producedaccording to the invention by drawing a wire of the. kind shown in FIG.2 through a circular die;

. FIG. 4 is a ribbed wire similar to that shown in FIG. 2 but providedwith obliquely pitched ribs, and

FIG. 5 diagrammatically illustrates the general layout of apparatus forproducing a reinforcing wire according to FIG. 3 from a rolled wire ofthe kind shown in FIG. 1.

A rolled wire 1 (FIG. 1) of circular section is drawn by a dog 2 insuccession through a shaping mill with a pair of rolls 3, 4 and a die ordrag plate 5 (FIG. 5). The rolls are provided with equidistantly spacedribs 30 and 4a and are coupled by intermeshing gear wheels 6 and 7 insuch a way that the ribs 3a and 4a will be alternately pressed intoopposite sides of the wire. The action of the rolls 3 and 4 is to deformthe rolled wire 1 into the shape illustrated in FIG. 2, that is to saythe cross section of the wire is deformed into an oval cross section(FIG. 2), indentations 8 being pressed into the flattened sides of theoval cross section leaving lands between neighbouring indentations,which form ribs 9, the ribs 9 on one side of the wire being staggered inrelation to the ribs 9 on the opposite side of the Wire by half thepitch of the ribs (FIG. 5). As the wire is immediately drawn through thedie 5 the cross section is reduced by about 15 to 50% and its lengthincreased accordingly by about 15 to 50% (FIG. 3). The diameter of theround section wire thus produced (FIG. 3) is approximately equal to orless than that of the circle (dotted line, FIG. 2) which can beinscribed between the indentations 8 in the wire section formed when thewire has been cold-formed by the rolls 3 and 4. The drawn wire isfinally straightened into bars on revolving straightening machines andthen cut to length in conventional manner.

The initial rolled wire (FIG. 1) may be a round steel wire having adiameter of 8.5 mm, a tensile strength of 40-45 kg./mm. a yield pointstress of 24-32 kg./mm. and an ultimate elongation of 25 to 30%. Afterhaving been cold rolled, the width b of the wire (FIG. 2) may be about 9mm. and its height it say 8 mm., its tensile strength being 48 to 50kg./mm. its yield point stress 30 to 38 kg./mm. and its ultimateelongation at fracture 5 to 7%, the indentations 8 having a maximumdepth of 0.5 mm. The pitch of the ribs 9 being about 10 mm., theindentations 8 may be 4 mm. and the ribs 6 mm. wide. After drawing, thewire (FIG. 3) may have a diameter d of 7 mm., a tensile strength of 60to 65 kg./mm. a yield point stress of 52 to 55 kg./mm. and an ultimateelongation of 8%. The drawing speed may be, for example, 2.5 meters/see,and the reduction about 40%. In other Words, if the pitch of the ribsbefore drawing was 10 mm. (FIG. 2), it will be 14 mm. (FIG. 3) after thedrawing. On the other hand, the depth of the indentations will have beenreduced from 0.5 mm. to 0.3 mm. The indentations or ribs on the drawnwire are quite sufficient for creating the required bond with theconcrete. By this procedure the strength and yield point stress of thewire has been considerably raised without reducing its colddeformability, whereas the depth of the indentations is sufficient togive an excellent bond in the concrete.

In the wire shown in FIG. 4, the indentations 8a rolled into the wireare obliquely placed in relation to the wire axis so that the crosssection of the wire will be substantially the same throughout itslength.

The ribs or indentations may also be of some other shape. For example,the surface of the rolled wire may be formed with round or polygonalindentations by hot or cold rolling, so that the resultant ribs will beof reticular pattern. If the drag plate has a circular opening and theribs are already produced in hot rolling the wire, it is advisable toimpart an oval cross section to the Wire as shown in FIG. 2.

The method proposed by the invention can naturally be applied to wiresof other cross sectional profile and other than circular drawing diescould be used.

What is claimed is:

1. A method of producing a reinforcing element comprising rolling spacedtransverse notches into a wire of substantially circular cross-section,and die-drawing the wire to a circular cross-section which is at mostapproximately equal to the cross-section of the largest concentriccircle which can be inscribed in the first said cross-section adjacent anotch.

2. A method as claimed in claim 1 comprising rolling said notches intoan oval wire.

3. A method as claimed in claim 1 comprising rolling said notches into acircular wire whereby flattening of said wire into oval shape occurs.

4. A method of producing a reinforcing element comprising rolling spacedtransverse notches in a wire of substantially circular cross-section,the depth of the notches and the deformation of the wire resulting fromsaid rolling being of a size to limit the stresses set up substantiallyto the surface of the wire, and then die-drawing the wire to a circularcross-section which is at most approximately equal to the cross-sectionof the largest concentric circle which can be inscribed in the firstsaid cross-section adjacent a notch.

5. A method of producing a reinforcing element comprising the step ofrolling spaced transverse notches into a wire of rounded circumference,the wire at the end of said rolling step remaining rounded on its entirecircumference and the depth of the notches and the deformation of thewire resulting from said step being of a size to limit the stresses setup substantially to the surface of the wire, and then die-drawing thewire to a circular cross-section which is at most approximately equal tothe cross-section of the largest concentric circle which can beinscribed in the first said cross-section adjacent a notch.

6. A method of producing a reinforcing element comprising the step ofrolling a wire of substantially circular cross-section into an ovalcross-section, while applying spaced transverse notches thereto, thedepth of the notches and the deformation of the wire resulting from saidstep being of a size to limit the stresses set up substantially to thesurface of the wire, and then die-drawing the wire to a circularcross-section which is at most approximately equal to the cross-sectionof the largest concentric circle which can be inscribed in the firstsaid cross-section adjacent a notch.

References Cited in the file of this patent UNITED STATES PATENTS1,929,695 Julien Oct. 10, 1933 1,930,446 Weybrecht Oct. 10, 19331,982,352 Richardson Nov. 27, 1934 2,036,034 Fulmer Mar. 31, 19362,078,434 Wise Apr. 27, 1937 2,260,779 Hoffman Oct. 28, 1941 2,333,238Finnie Nov. 2, 1943 2,335,418 Johnson Nov. 30, 1943 FOREIGN PATENTS728,636 Great Britain Apr. 20, 1955 OTHER REFERENCES WireDrawing and theCold Working of Steel; A. T. Adam, 1926, pages 97-144, H. F. and G.Witherby, London.

Design of Machine Elements: M. F. Spotts, 2nd edition 1953, pages 68,69, and 472 relied upon, Prentice Hall, New York, NY.

Metals Handbook, (1948), Published by ASM, Cleveland, Ohio, pages 536and 537 relied upon.

1. A METHOD OF PRODUCING A REINFORCING ELEMENT COMPRISING ROLLING SPACEDTRANSVERSE NOTCHES INTO A WIRE OF SUBSTANTIALLY CIRCULAR CROSS-SECTION,AND DIE-DRAWING THE WIRE TO A CIRCULAR CROSS-SECTION WHICH IS AT MOSTAPPROXIMATELY EQUAL TO THE CROSS-SECTION OF THE LARGEST CONCENTRICCIRCLE WHICH CAN BE INSCRIBED IN THE FIRST SAID CROSS-SECTION ADJACENT ANOTCH.